35 Why I can't divide by y in this equation: 4y = y? 34 Sequence that is neither increasing, nor decreasing, yet converges to 1 33 Is this proposed method of finding primes valid? If so, would it be effective? 20 Is any mathematican more famous for their conjecture(s) than their theorem(s)? 14 Is there an explicit formula that gives the value of $\sqrt{2+\sqrt{2+\sqrt{2+\cdots}}}$ for $n$ square roots?

### Reputation (15,418)

 +10 Building a cube from small bricks such that no lines can be pushed through between the seams +40 Show that $xy$ cannot be written as a polynomial in $x+y$ and $x^2+y^2$ +10 Is this proposed method of finding primes valid? If so, would it be effective? +10 If $|a_n| \to |a|$ and $|\frac{a_n}{|a_n|}-\frac{a}{|a|}|\to0$ can we conclude $a_n\to a$?

### Questions (25)

 15 Killing Flies with a Checkerboard Flyswatter 12 Groups with no small nontrivial representation 12 Minimum area contained between measurable set and translate by $\lambda$: A strengthening of 2018 USA TSTST #9 8 Proof of Cayley-Hamilton Theorem in infinite fields only? 6 Is $f(x)$ necessarily a polynomial if $f(f(x))$ is?

### Tags (260)

 174 elementary-number-theory × 75 72 real-analysis × 43 169 sequences-and-series × 65 67 calculus × 33 151 algebra-precalculus × 44 66 polynomials × 32 136 number-theory × 70 57 limits × 26 114 prime-numbers × 33 53 geometry × 29

### Bookmarks (43)

 73 If $a+b=1$ so $a^{4b^2}+b^{4a^2}\leq1$ 63 How and why does Grothendieck's work provide tools to attack problems in number theory? 53 To evaluate $\int_0^{+\infty} \frac{\;\mathrm dx}{\sqrt{x^3+a^3}\sqrt{x^3+b^3}\sqrt{x^3+c^3}}$ 53 Crazy pattern in the simple continued fraction for $\sum_{k=1}^\infty \frac{1}{(2^k)!}$ 49 Proof (claimed) for Riemann hypothesis on ArXiv [closed]